That which is done or doing; the exercise of power, or the effect, of which power exerted is the cause; a performance; a deed.

That best portion of a good man's life,
His little, nameless, unremembered acts
Of kindness and of love.
Wordsworth.

Hence, in specific uses: (a)

The result of public deliberation; the decision or determination of a legislative body, council, court of justice, etc.; a decree, edit, law, judgment, resolve, award; as, an act of Parliament, or of Congress.

(b)

A formal solemn writing, expressing that something has been done.

Abbott. (c)

A performance of part of a play; one of the principal divisions of a play or dramatic work in which a certain definite part of the action is completed.

(d)

A thesis maintained in public, in some English universities, by a candidate for a degree, or to show the proficiency of a student.

2.

A state of reality or real existence as opposed to a possibility or possible existence.

[Obs.]

The seeds of plants are not at first in act, but in possibility, what they afterward grow to be.
Hooker.

3.

Process of doing; action. In act, in the very doing; on the point of (doing).

"In act to shoot."

Dryden.

This woman was taken . . . in the very act.
John viii. 4.

Act of attainder. Law See Attainder. -- Act of bankruptcyLaw, an act of a debtor which renders him liable to be adjudged a bankrupt. -- Act of faith. Ch. Hist. See Auto-da-F'e. -- Act of GodLaw, an inevitable accident; such extraordinary interruption of the usual course of events as is not to be looked for in advance, and against which ordinary prudence could not guard. -- Act of grace, an expression often used to designate an act declaring pardon or amnesty to numerous offenders, as at the beginning of a new reign. -- Act of indemnity, a statute passed for the protection of those who have committed some illegal act subjecting them to penalties. Abbott. -- Act in pais, a thing done out of court (anciently, in the country), and not a matter of record.

To perform actions; to fulfill functions; to put forth energy; to move, as opposed to remaining at rest; to carry into effect a determination of the will.

He hangs between, in doubt to act or rest.
Pope.

3.

To behave or conduct, as in morals, private duties, or public offices; to bear or deport one's self; as, we know not why he has acted so.

4.

To perform on the stage; to represent a character.

To show the world how Garrick did not act.
Cowper.

To act as ∨ for, to do the work of; to serve as. -- To act on, to regulate one's conduct according to. -- To act up to, to equal in action; to fulfill in practice; as, he has acted up to his engagement or his advantages.